Dummy Bonding Pad Layout for Uniform Underfill in Fan-Out Packages
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Solution Overview
Problem
In semiconductor die packaging, the interfaces between fan-out wafer level packages and underfill material portions experience mechanical and thermal stresses, leading to crack formation in the underfill material, which can induce additional cracks in the semiconductor die and other components, affecting the reliability of the package.
Innovation Solution
The use of dummy metal bonding structures and dummy solder material portions enhances the capillary force during underfill material application, ensuring uniform distribution and reducing void formation in die-to-die or die-to-package gaps, thereby preventing cracks and improving the reliability of the underfill material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If underfill material is applied to fill gaps between semiconductor dies and package substrate, then void formation is reduced and uniform distribution is achieved, but crack formation occurs at interfaces due to mechanical and thermal stress
Solution Approach 1:
The patent applies underfill material to the package substrate before attaching the semiconductor dies, rather than after. This preliminary application allows the underfill to be uniformly distributed in the gaps between dies and substrate, and the dummy bonding pads are pre-formed to enhance capillary force during this initial underfill application, preventing void formation and reducing subsequent crack formation
Solution Approach 2:
The patent introduces dummy metal bonding pads as intermediary structures between the real bonding pads and the underfill material. These dummy pads enhance the capillary force that draws underfill material into the gaps, ensuring uniform distribution while the entire structure (including dummy pads) acts as a stress-distributing intermediary that reduces crack formation at critical interfaces
2Manufacturing precision
If dummy metal bonding structures are added to enhance capillary force, then underfill material distribution is improved and void formation is reduced, but device complexity increases
Solution Approach 1:
The dummy metal bonding pads serve multiple functions: they enhance capillary force for underfill material application, maintain the bonding pad array's geometric uniformity, and act as stress-distributing elements. By making these dummy structures multi-functional, the patent justifies their addition despite increased structural complexity, as they simultaneously improve underfill distribution and reduce crack formation
Solution Approach 2:
The patent creates dummy metal bonding pads that are copies of the real bonding pads in terms of geometry, material composition, and arrangement. These copied structures replicate the capillary force-enhancing properties of real pads without requiring electrical connections to semiconductor dies, thus improving underfill distribution while adding minimal functional complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The enhanced capillary force ensures uniform underfill material distribution, reduces void formation, and increases the reliability of the semiconductor package by minimizing crack formation and solder bridging, thus enhancing the structural integrity of the package.
Implementation Method 1
The use of dummy metal bonding structures and dummy solder material portions enhances the capillary force during underfill material application, ensuring uniform distribution and reducing void formation in die-to-die or die-to-package gaps
Data Source
AI summary
A fan-out package includes a redistribution structure having redistribution-side bonding structures, a plurality of semiconductor dies including a respective set of die-side bonding structures that is attached to a respective subset of the redistribution-side bonding structures through a respective set of solder material portions, and an underfill material portion laterally surrounding the redistribution-side bonding structures and the die-side bonding structures of the plurality of semiconductor dies. A subset of the redistribution-side bonding structures is not bonded to any of the die-side bonding structures of the plurality of semiconductor dies and is laterally surrounded by the underfill material portion, and is used to provide uniform distribution of the underfill material during formation of the underfill material portion.